1. The problem is to find the relative formula mass of water (H₂O). 2. The relative atomic masses are given: hydrogen (H) = 1, oxygen (O) = 16. 3. The formula for relative formula mass is the sum of the relative atomic masses of all atoms in the molecule. 4. Water has 2 hydrogen atoms and 1 oxygen atom. 5. Calculate the total mass: $$2 \times 1 + 1 \times 16 = 2 + 16 = 18$$. 6. Therefore, the relative formula mass of water is 18.